Circuit breaker with improved contact arm stop



June 28, 1966 H, W- ARCHER ET AL 3,258,572

CIRCUIT BREAKER WlTHy IMPROVED CONTACT ARM STOP Filed Jan. '7, 1965 FIG.1

INVENTORS /(ENNE TH d. Sra/ 55, HA RR Y W. A RCHER ATTORNEY United States Patent O CIRCUIT BREAKER WlTH IMPROVED CONTACT ARM STOP Harry W. Archer, New Britain, and Kenneth J. Stokes,

Wethersfield, Conn., assignors to General Electric Company, a corporation of New York Filed Jan. 7, 1965, Ser. No. 423,969 7 Claims. (Cl. 200-166) 'Ithis invention relates to multipole circuit breakers of substantial current carrying capacity and more particularly to an improved component lfor such multipole circuit breakers comprising a combined insulating barrier and movable contact arm stop.

Circuit breakers of tthe type referred to usually have a plurality of movable contact arms supporting movable electrical contacts adapted to electrically engage stationary electrical contacts. Such movable contact arms are usually spring-loaded for .actuation about a pivotal axis and cir- -cuit breaking, current interruption actuation may be affected either by an external, reciprocally operated handle which is mechanically connected to the movable Contact ,arms through suitable linkage or by automatic actuation through a trip mechanism which is responsive to overload current conditions. Under extreme `overload conditions the movable contacts may be blown apart from the stationary .contacts of the circuit breaker by the force of the arc between the contacts when the circuit breaker is actuated and initially opened. The force of the contacts being blown apart in this manner, it has been found will impart considerable momentum to the movable contact arms and when suddenly brought to a stop at the end of their full arcs of movement, the movable contact arms may be distorted or take a permanent set, causing changes in pre-established operating functions unless so-me means or expedient is employed to prevent such distortion or permanent set occurring in the movable contact arms.

Additionally, it has been found desirable in such circuit breakers to have insulating barriers positioned and supported in pole chambers ofthe circuit beraker to separate the main current carrying contacts `from the remainder of the circuit breaker. Such a barrier isolates the extreme arcing which occurs under excessive overload conditions upon opening of the main current carrying contacts and helps to minimize the contamination of the trip mechanism and its associated moving parts in the remainder of the circuit breaker.

It is the primary object of the present invention to combine in a single, unitary structure the functional properties of both a pole chamber insulating barrier and a movable contact arm stop.

It is another object of the present invention to provide a single, combined, unitary, pole chamber insulating barrier and movable contact arm stop for a multipole circuit breaker of substantial current carrying capacity.

Another object of the present invention is to provide such a combined pole ,chamber insulating barrier and movable contact arm stop which is mechanically strong and inexpensive to manufacture as well as being heat resistant and having excellent dielectric properties.

Another object of the present invention is to provide a unitary movable contact arm stop which functions as an insulating barrier in a pole chamber `and also includes means for relieving extreme pressures which may be built up in the pole chamber under excessive arcing conditions.

Yet another object of the present invention is to provide a combined insulating barrier fora pole chamber and a movable contact arm stop which is separate from the insulating casing of the casing of the circuit breaker so as to facilitate and expedite desirable manufacturing proc- 3,258,572 Patented June 28, 1966 ice esses in the fabrication of such insulating casings for the circuit breaker.

Our invention in one form comprises a generally planar member of mechanically strong, highly dielectric material configured and dimensioned to be received and supported in a pole chamber of the insulating casing of a circuit breaker. In its preferred embodiment the combined insulating barrier and movable contact arm stop of the present invention may have an outside form defined by a bottom edge and side edges joined in right angular relationship and including upper side edges which are ang-ularly included to meet a top edge that is substantially parallel to the bottom edge. A first aperture is disposed in the member and adapted to receive a movable contact ar-m therethrough. The combined insulating barrier and movable contact arm stop may also include a second aperture therethrough which is designed and dimensioned to relieve extreme pressures which may be built up in a pole chamber upon the opening of electrical contacts under excessive overload current conditions. The combined insulating barrier and movable contact arm stop of the present invention may be slidingly received in a slotted portion of the walls of the lower part of the insulating casing of a multipole circuit breaker which divide it into pole chambers so that its upper angularly inclined edges extend beyond the' walls o-f the lower part of the circuit breaker insulating casing and are similarly slidingly re-` ceived in slotted and appropriately reinforced portions of the upper portion of the circuit breaker insulating ca sing comprising the upper part of the pole chamber. The cornbined circuit breaker member of the present invention thus coniigured and received and supported in the insulating casing of a multipole circuit breaker, performs the function of isolating a portion of the pole chamber in which it is so positioned and functionally coacts with operatively related portions of the circuit breaker assembly to provide a desirable form of movable contact arm stop.

Additional objects and aspects of the invention will be more -fully understood from the following detailed description and the accompanying drawings and its scope will be pointed out in the appended claims.

In the drawings:

FIGURE 1 is a partially cross-sectional side view of a circuit breaker embodying a form of the present invention as one of its members;

FIGURE 2 is a perspective, partial view illustrating the manner in which embodiments of the present invention are positioned and disposed in a multipole circuit breaker;

FIGURE 3 is a plan view o-f a portion of a multipole circuit breaker showing in sectional view an embodiment of the present invention positioned therein.

Referring n-ow to FIGURE 1, there is illustrated a multipole circuit breaker shown generally at 10 and having an external handle 11 reciprocally operable from the off position as shown by the solid lines to the on position as illustrated by the dash lines. The circuit breaker 10 is enclosed in an insulating casing or housing lcomprising an upper portion 12 and a lower portion 13 which may typically be of a molded dielectric material. The upper portion 12 and the lower portion 13 of the insulating casing of the circuit breaker are joined along congruent planar edges designated generally at 14.

It has been found that molded dielectric materials may in the course of manufacture become warped or distorted so as to deviate slightly from a desired configuration such as a perfectly flat, planar edge. For that reason frequently the manufacturing process for the top yand bottom edge portions of an insulating casing for a multipole circuit breaker includes finishing by belt sanding or other suitable methods to provide truly flat, planar edges and insure the tight and secure tit between two planar convskill-ed in the art.

gruent edges such as those shown at 14. This step in the manufacture and fabrication of insulating casings for multipole circuit breakers, while being effective and expedient to insure their proper fit with each other, nonetheless obviates Ian expedient for providing a mov- Iable contact arm stop which will be apparent to those It has been suggested that the top insulating casing portion for ia circuit breaker include a wall member extending downwardly to a point at which Vit is desirable to interrupt the travel of the movable contact arm upon its actuation to interrupt current flow under overload conditions. While this is an obvious and apparently simple expedient, it introduces another problem in that the addition of a member which extends beyond the sidewalls of the upper portion of `the insulating casing and beyond the congruent planar edges which join with the comparable portion of the lower part of the insulating casing, precludes the use of accepted, conventional and economical manufacturing methods and procedures to nish the joining edges of the upper and lower portions of the insulating casing, such as power s-anding, lfor instance.

The present invention obviates this problem in that no such extending portion is required as a mechanical stop for the movable contact arms :and the upper and lower portions of the insulating casing of the circuit breaker need only have an appropriately slotted and reinforced portion to slidingly receive and Asupport the planar member which comprises the present invention. The circuit breaker of FIGURE 1 `further includes an appropiate spring-loaded toggle mechanism operably connected with the handle 11 and being adapted to engage and latch with a tripping mechanism 16. The tripping mechanism 16 is responsive to automatic actuation by either Va thermally or magnetically :sensitive device 17 which operates to trip the trip mechanism upon the occurrence of overload conditions of current flow through the circuit breaker. Typical of the movable contact arm assemblies used in such multipole circuit breakers is that 'shown in FIG- URE l wherein the movable contact 18 is carried by a contact supporting member 19 which in turn is pivotally A connected by a pivot pin Z1. to a generally channel shaped contact -arm 2t). The kforward end of the movable contact support 19, has a post 22 affixed thereto and extending through a slot 23 in the end of the contact arm 20. A compression spring 24 is positioned on and about the post 22 between the contact support 19 and the contact arm 2t) and a washer and cotter pin or other suitable retaining means 25 limits the movement of the contact arm away from the contact support 19 Eand also retains the spring 24 under compression so that the contact 18 is effectively spring biased into engagement with the stationary contact 26.

The contact arm 20 is pivotally supported on a pivot pin 27 passing through depending side portions of the contact arm 2t) and h-aving its ends journaled in opposed side portions of a stationary frame member axed to and supported by the bottom portion of insulating casing of the circuit breaker. The circuit breaker assembly of FIGURE 1 also includes Van arc extinguishing structure which may comprise stacked arc extinguishing plates of ceramic or steel as shown generally at 29 and positioned in the pole chamber adjacent the stationary contact and the movable contact 18 for the purpose of minimizing, suppressing and extinguishing the arc which is created by the flow of heavy overload currents between the movable contact 18 and the stationary contact 26 when those contacts are parted to interrupt the overload currents in the main conductors of the circuit breaker. The combined insulating barrier and movable contact arm stop of the present invention is shown in cross-sectional view at 28 in FIGURE l positioned and supported in the insulating casing 12 of the circuit breaker 10 and having an laperture through which the movable Contact arm assembly is positioned. The complete configuration of `it is in engagement with the stationary contact.

the combined insulating barrier and movable contact arm stop may be seen in its entirety in the perspective view of FIGURE 2.

FIGURE 2, it will be appreciated, is a partial perspecltive view of that portion of an interior circuit breaker assembly which may include several combined insulating barriers and movable contact arm stops of the present invention. Accordingly, the illustration is not intended to represent an entire operable assembly, but rather to illustrate the contiguration of the circuit breaker member of the present invention in its preferred embodiment and to show the manner in which the combined insulating barrier and contact arm stop is positioned and co-acts with respect to certain other members of a typical multipole circuit breaker assembly, and particularly with respect to the movable contact arms and the Ipole chambers of such a circuit breaker. The illustration of FIG- URE 2 is 'therefore fragmentary for the purpose of simplicity and clarity.

There is shown a portion of the internal assembly of a three pole circuit breaker arrangement comprising three adjacent and spaced movable contact arm assemblies 30, 31. and 32 substantially of the type previously described in connection with FIGURE 1, and joined through suitable fastening means 33, 34 and 35 -to a common contact cross arm 36 of reinforced insulating material. Movement of any one of the contact arm assemblies 30, 31 or 32 therefore carries with it the other two contact arms preventing what is known as single phasing. The centrally positioned contact arm assembly 31 is shown as having a cradle pivot pin 37 positioned immediately above it which would be suitably supported in the cornplete circuit breaker assembly and upon opening of the contact arms, the Contact arm assembly 31 will engage the cradle pin 37. Accordingly, there is shown at 38 an insulating barrier which does not perform a movable contact arm stop function. However, the insulating barriers 39 and 4t? on either side of the central contact arm are congured in accordance with the concept of the present invention and perform the dual function of insulating 'barriers and contact arm stops in a manner which will now be explained.

Assuming that the circuit breaker is positioned in its on position, i.e., the movable contact arms are positioned `so as to engage the movable contacts in spring-biased contact with their respective aligned stationary conta-cts, upon the flow of overload current through the main conductors of the circuit breaker in excess of the circuit breakers ampere rating, the trip mechanism will be actuated by either a thermally responsive or magnetically responsive device generally shown at 17 in FIGURE l and the latched, spring-loaded contact arm assemblies will be released causing the movable Icontacts to move away from the stationary contacts, interrupting the flow of overload current. When such overload current is excessive, the arc that results from the flow of current between the movable and stationary contact upon their immediate opening is so intense as to build up pressures in the respective pole chambers of the circuit breaker and blow apart the contacts with considerable force. Notwithstanding the effect-of the arc extinguishing structure such as shown at 29 in FIGURE 1, considerable momentum is imparted to the movable contact arm assembly and if appropriate means are not provided to expend such momentum, the movable contact arms may be bent, distorted or take a set which in turn will change the amount and degree of spring bias action exerted by the movable contact arm assembly upon the movable contact when The present invention provides preventative means in the form of a movable Contact arm stop which also functions as an insulating barrier and as can be seen from FIGURES 1 and 2, when the movable contact arms are sprung apart from the stationary contacts by release of the latched spring linkage under overload conditions they move rapidly in a snap action and the movable contact arm assemblies 30 and 32 as shown in FIGURE 2, strike the upper portion of the combined insulating barrier and movable contact arm stop 39 and 40, respectively. As may readily be seen from FIGURE 1 the contact arm assembly, upon striking the upper portion of the combined insulating barrier and movable contact arm stop as at 28, expends the momentum of the assembly by the compression of the spring 24 whereby the movable contact arm and the movable contact arm support 19 :are not bent, distorted nor do they take a set, thereby insuring that the amount of spring bias exerted by the movable contact 18 upon engagement with the stationary contact 26 is and remains the same as originally designed and established.

Referring now to FIGURE 2 it will be seen that the above described action takes place with both of the movable contact arm assemblies 30 and 32 and their associated combined insulating barriers and movable contact .arm stops 39 and 40, respectively, while the centrally positioned movable contact assembly 31 strikes the cradle pivot pin 37 which performs a stop function. As may be seen in FIGURE 2 the form of combined insulating barrier and movable contact arm stop 39 has a substantially rectangular aperture 31 to receive a movable contact arm assembly therethrough and has an outer configuration defined by a bottom edge joined with side edges at right angles and an upper pair of side edges angularly inclined to meet a top edge which -is parallel with the bottom edge. The combined insulating barrier and movable contact arm stop of the present invention substantially configured as shown in FIGURE 2 is received into a pole chamber of a circuit breaker insulating casing of the type previously described in connection with FIGURE 1, fitted in suitably slotted and reinforced portions in the upper and lower parts of the insulating casing to position and support the insulating barrier and movable contact arm stop member. Upon the movable contact arm assembly .striking the insulating barrier and movable contact arm stop in its pole chamber, the angularly inclined side edges on the upper portion of the insulating barrier and movable contact arm stop tend to distribute the forces of momentum of the movable contact arms throughout the casing by reason of such angular disposition and theerfore aid the absorption of such forces without damage to the circuit breaker and without disturbing its adjusments.

Additionally, each of the insulating barriers and movable contact arm stops 39 and 40 as shown in FIGURE 2 have an additional aperture such as shown at 44 and 46 adapted and conceived to relieve extraordinary pressures which may build up in a pole chamber as a result of extreme arcing caused by excessive overcurrent conditions upon interrupting the current iiow by opening the movable contacts from engagement with the stationary contacts of the circuit breaker.

It will be understood and appreciated by those skilled in the art that the movable contact arms of a circuit breaker of the type with which the present invention concept is concerned do not strike the lcombined insulating barrier and movable contact arm stop upon each opening of the circuit breaker. For instance, when the circuit breaker is manually actuated to interrupt the ow of currents therethrough by means of the externally operable handle, the movable contact arm assemblies will ordinarily not strike the contact arm stop. Similarly, under normal conditions of operation when the circuit breaker is actuated to interrupt marginally overloading conditions, the movable contact arm assemblies will not strike the contact arm stops. However, under conditions fof extreme and excessive overloading, the contacts of the circuit breaker may be blown apart with considerable force and the contact arm stops will interrupt their travel, distributing and absorbing the kinetic energy of the movable contact arm assemblies.

iFIGURE 3 is a partial plan view of the bottom portion of the multipole circuit breaker shown in FIGURE 1. The bottom portion of the circuit breaker insulating casing 13 is divided by wall partitions such as that shown at 51 in-to several pole -chambers only one of which is shown in a partial view of FIGURE 3. The movable contact arm assembly comprising the movable contact supportl19 and movable contact arm 2t)` and its associated members is shown disposed in a pole chamber of the circuit breaker and positioned through the aperture in the combined insulating barrier and movable contact arm stop 28, illustrated in a sectional view taken through the plane at which the top and bottom portions of the insulating casing meet. As may be most clearly seen strom IFIGURE 3, the com- 'bined insulating barrier and movable contact arm stop 28 of the present invention is slidingly received and supported in slotted, fitted portions of the insulating casing, las shown as 52 and 53. Thus the combined insulating barrier and movable contact arm stop 28 is suitably positioned in the insulating casing, supported by it and disposed so as to distribute and absorb within the entire assembly the momentum of the movable contact arm assembly when it is actuated under excessive overload conditions. Moreover, the combined insulating barrier and contact arm stop of the presen-t invention isolates that portion of lt-he pole chamber where ancing may accur, deterring contaminants from coming into contact with the movable members of the trip mechanism and the handle operating linkage'. The provision of the secondary aperture in the combined insulating barrier and movable contact arm stop provides adequate relief of extraordinary pressures which may be built up in the isolated portion of a pole chamber due to severe arcing under excessive overload conditions.

Thus, our inventive concept because of its configuration, lends itself readily to embodiment in a structure which has the requisite mechanical strength when fabricated of materials which are both heat resistant, and have excellent dielectric qualities. `Gur combined insulating barrier and movable arm stop is inexpensive, may be manufactured by conventional methods and machinery, and possesses the added advantage of accommodating and facilitating the continued use of proven conventional manufacturing processes in iinishing the planar edges of molded circuit breaker insulating casings.

While we have disclosed only certain embodiments of the invention, it will be readily appreciated that many modifications thereof may be made. We therefore intend by the appended claims to cover all such modifications as fall within the true spirit and scope of the invention.

What we claim as new and desire -to secure by Letters Patent of the United States is:

1. A combined insulating barrier and movable contact arm stop Vfor a circuit breaker having a movable contact arm comprising a planar insulating member configured and dimensioned to 'be received and supported in the insulating casing of said circuit breaker, yand an aperture in said insulating member adapted `to receive said movable contact arm therethrough, said aperture having a dimension along the plane of movement of said movable contact arm such that the upper portion of said insulating member will eng-age said movable contact arm short of its full arc of movement.

2. A combined insulating barrier and movable contact .arm stop for a circuit breaker having a movable contact arm comprising a planar insulating member configured and dimensioned to be received and supported within the insulating housing of said cir-cuit breaker, and a generally polygonal aperture in said insulating member adapted to receive said movable vcontact arm therethrough, said aperture having a dimension along the plane of movement of said movable contact .arm such that the upper portion of said insulating member will engage said movable contact arm short of its full arc of movement.

3. A combined insulating barrier and contact arm stop for a circuit breaker having at least one pivoted, springloaded contact arm, comprising a rigid planar insulating member congured and dimensioned to be received and supported within the insulating housing of `said circuit breaker, and a generally polygonal aperture in said insulating member adapted to receive said contact arm therethrough, said insulating member being adapted to be positioned between the pivoted axis and the contact of said contact arm such that the upper portion of said insulating member Will be engaged by said contact arm short of its full arc of movement.

4. A combined insulating barrier and movable contact arm stop for a multipole circuit breaker having a movable contact arm comprising a planar insulating member configured and dimensioned to be received and supported within a pole chamber of lthe insulating housing of said circuit breaker, a first Igenerally polygonaly aperture in said insulating member adapted to receive said movable contact arm therethrough, said aperture having a dimension along the plane of movement of said movable contact arm such that the upper portion of said insulating member will engage said movable contact arm short of its full 'arc of movement upon opening, and a second aperture in said insulating member adapted to relieve pressures built up in said pole chamber upon the opening of the contacts of said circuit breaker.

5. A combined insulating barrier and movable contact arm stop fora multipole circuit breaker having a movable contact arm comprising a planar insulating member having a .bottom edge joined by lower side edges at right angles, upper side edges angularly inclined inwardly and joined to a top edge parallel to said bottom edge, said planar insulating member being dimensioned to be received and supported Within a pole chamber of the insulating housing of said circuit breaker, a rst generally polygonal aperture in said insulating member Iadapted 4to receive said movable contact arm therethrough, said aperture having a dimension along the plane of movement of said movable contact arm such that the upper portion of said insulating member will engage said movable contact arm short of its full are of movement upon opening, and a second aperture in said insulating member positioned above said first aperture and adapted to relieve pressures built up in said pole chamber upon the opening of the contacts of said circuit breaker.

6. In a multipole circuit breaker having a plurality of spring-loaded movable contact arms operable from a closed position through an arc of movement to an open position, at least one contact arm stop and insulating barrier comprising a plan-ar insulating member configured and dimensioned to be received and supported within a pole chamber of the insulating housingof said circuit breaker, and a generally rectangular aperture in each said insulating member ,adapted to receive one of said springloaded contact arms therethrough, each said aperture having a maximum dimension along the plane of movement of the movable contact arm positioned therethrough such that the upper portion of said insulating member will engage said movable contact arm short of its full arc of movement.

7. In a multipole circuit breaker having a plurality of snap-action movable contact arms operable from a closed position through an arc of movement to an open position, at least one contact tarm stop and insulating barrier, each comprising Ia planar insulating member having a bottom edge joined by lower side edges at right angles, upper side edges angularly inclined inwardly and joined to a top edge parallel to said bottom edge, said planar insulating member being dimensioned to be received and supported within a pole chamber of the insulating housing of said circuit breaker, a rst generally polygonal aperture in said insulating member adapted to receive one of said movable contact arms therethrough, said aperture having a dimension along the plane of movement of said movable contact arm suc-h that the upper portion of said insulating member will engage said movable contact arm short of its full arc of movement upon opening, and -a second aperture in said insulating member adapted to relieve pressures built up in said pole chamber upon the opening of the contacts of said circuit breaker.

No references cited.

ROBERT K. SCHAEFE-R, Primary Examiner. 

1. A COMBINED INSULATING BARRIER AND MOVABLE CONTACT ARM STOP FOR A CIRCUIT BREAKER HAVING A MOVABLE CONTACT ARM COMPRISING A PLANAR INSULATING MEMBER CONFIGURED AND DIMENSIONED TO BE RECEIVED AND SUPPORTED IN THE INSULATING CASING OF SAID CIRCUIT BREAKER, AND AN APERTURE IN SAID INSULATING MEMBER ADAPTED TO RECEIVE SAID MOVABLE CONTACT ARM THERETHROUGH, SAID APERTURE HAVING A DIMENSION ALONG THE PLANE OF MOVEMENT OF SAID MOVABLE CONTACT ARM SUCH THAT THE UPPER PORTION OF SAID INSULATING MEMBER WILL ENGAGE SAID MOVABLE CONTACT ARM SHORT OF ITS FULL ARC OF MOVEMENT. 